Chiral ionic liquids based on nicotine for the chiral recognition of carboxylic acids

The synthesis of enantiopure ionic liquids based on (−)-nicotine is discussed. The desired compounds were prepared in good yields from (−)-nicotine via quaternization of the pyridine ring of (−)-nicotine with MeI and EtBr. After anion metathesis the ionic liquids were investigated as chiral solvating agents and showed a splitting of the signals of Mosher’s acid and mandelic acid in the 1H and 19F NMR spectra. In addition to aprotic solvents it was also possible to use methanol in the experiments.

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(S)-1-Methyl-3-(1-methylpyrrolidin-2yl)pyridinium bis(trifluoromethylsulfonyl)imideC13H17N3S2O4F6Ee = 100%[α]D20=-70.2 (c 1.14, CHCl3)Source of chirality: chiral poolAbsolute configuration: (S)

(S)-1-Methyl-3-(1-methylpyrrolidin-2yl)pyridinium hexafluorophosphateC11H17N2PF6Ee = 100%[α]D20=-83.7 (c 1.47, MeOH)Source of chirality: chiral poolAbsolute configuration: (S)

(S)-1-Methyl-3-(1-methylpyrrolidin-2yl)pyridinium tetrafluoroborateC11H17N2BF4Ee = 100%[α]D20=-102.4 (c 1.02, MeOH)Source of chirality: chiral poolAbsolute configuration: (S)

(S)-1-Ethyl-3-(1-methylpyrrolidin-2-yl)pyridinium bromideC12H19N2BrEe = 100%[α]D20=-116.8 (c 1.03, CHCl3)Source of chirality: chiral poolAbsolute configuration: (S)

(S)-1-Ethyl-3-(1-methylpyrrolidin-2-yl)pyridinium bis(trifluormethylsulfonyl)imideC14H19N3O4S2F6Ee = 100%[α]D20=-62.4(c 3.24, CHCl3)Source of chirality: chiral poolAbsolute configuration: (S)

(S)-1-Ethyl-3-(1-methylpyrrolidin-2-yl)pyridinium hexafluorophosphateC12H19N2PF6Ee = 100%[α]D20=-85.2(c 2.02, CHCl3)Source of chirality: chiral poolAbsolute configuration: (S)

(S)-1-Ethyl-3-(1-methylpyrrolidin-2-yl)pyridinium tetrafluoroborateC12H19N2BF4Ee = 100%[α]D20=-101.5 (c 2.65, CHCl3)Source of chirality: chiral poolAbsolute configuration: (S)